This invention relates to a process for producing aluminum hydroxide powder which makes it possible to obtain a filler-containing resin composition having an improved transparency, aluminum hydroxide aggregated particles which are the material therefor, a process for producing the same, and a vessel used therefor.
Aluminum hydroxide powder is often used as a filler for resins, such as unsaturated polyester resin, in producing artificial marble and the like. When aluminum hydroxide powder is used as a filler for artificial marble and the like, the powder is required to be excellent in filling property for resins and, at the same time, not to impair the transparency of resulting resin composition.
As to an industrial process for producing aluminum hydroxide, there are hitherto been known a process which comprises hydrolyzing a supersaturated aqueous sodium aluminate solution in the presence of seeds. For example, JP 63-23131 B discloses a process which comprises connecting plural vessels in series, feeding a supersaturated aqueous sodium aluminate solution continuously to the first vessel, hydrolyzing the supersaturated aqueous sodium aluminate solution in the presence of seeds, and allowing hydrolysis to proceed while sending the solution successively to the second vessel and the third vessel, to obtain aluminum hydroxide.
However, even when the aluminum hydroxide obtained by the above-mentioned process is filled in resins, it has been impossible to obtain a resin composition having a sufficient transparency.
The object of this invention is to provide aluminum hydroxide aggregated particles which can be suitably used for producing aluminum hydroxide powder which can give a resin composition that shows a high transparency when filled in resins or the like, a process for producing the aggregated particles, a vessel used therefor, and a process for producing aluminum hydroxide powder which uses the aggregated particles.
The reference numerals in the Figures signify the following.
1 concentrating region, 2 clarifying region, 3 vessel, 4 baffle plate, 5 stirring blades, 6 rotating shaft, 7 stirrer, 8 sweeper, 9 offtake port, 10 anticorrosive material, 11 straightening vane